1. Field of the Invention
Embodiments of the invention generally relate to control of layer property over the surface of a substrate useful for fabricating into display devices.
2. Description of the Related Art
For years, cathode ray tube (CRT) technology is used to make devices, such as TV screens or monitors, with great colors and high-quality pictures. Unfortunately, CRT devices are bulky and heavy, and can not be manufactured into large sizes. The demands for flat screens in large size have resulted in great advancement in the technologies of Liquid Crystal Display (LCD), Plasma Display Panels (PDP), Field Emission Display (FED), Organic Light Emitting Diode (OLED), and other flat panel display technologies. Recently, a flat panel screen technology, called Surface-conduction Electron-emitter Display (SED) has also emerged. SED devices use millions of Surface-conduction Electron Emitters (SEC) in miniaturized sizes as electron emitters instead of one big CRT tube
Fabrication of these display devices, usually on large area substrates, such as glass substrates, requires deposition and etching of multiple layer layers with each layer serving different function. In general, the substrate for device fabrication is subjected to various processes, such as chemical vapor deposition (CVD), sputtering, physical vapor deposition (PVD), lithography, etching, ion implantation, ashing, cleaning, heating, annealing, and the like in a specific multi-step fabrication sequence to process layers of metal and silicon containing layers thereon. One example of a multilayer layer stack is a thin layer transistor (TFT) structure useful for fabricating LCD and other devices.
Since the structures for various display devices and applications are distinct, it is important to control etch rates and etch profiles for various deposited layers on a surface of a substrate in order to generate a required final structure. FIGS. 1A-1D illustrate etching of a material layer 110 on a surface of a substrate 101 having a typical etching profile without any etching taper angle. As shown in FIG. 1A, the material layer 110 is deposited over the surface of the substrate 101 inside a deposition processing chamber. In FIG. 1B, a photoresist 112 can be deposited in accordance with a desired pattern over the material layer 110 during fabrication of a device structure.
In FIG. 1C, pattern etch is performed on the substrate 101 placed inside an etch chamber or in a wet etch solution to etch the material layer 110 into a feature 150, resulting in side walls 152 of the etched feature of the material layer 110 being straight with an etch angle α of zero degrees. Next, as shown in FIG. 1D, the photoresist 112 can be removed for continued substrate processing and the resulting material layer 110 exhibits a typical straight etch profile over the feature 150. As device structures continues to evolve and vary among different display applications, it is desirable to control etching of a material layer into concave, convex, or taper etch profiles of the features over a defined mesa or pattern.
Therefore, there remains a need for a method and apparatus to process one or more layers with controlled etch profile.